Copper alloy



Patented Nov. 8, 1938 UNITED STATES COPPER ALLOY Franz R. l-lensel and Earl I. Larsen, Indianapolis,

Ind., assignors to P. R. Mallory & 00., Inc., Indianapolis, Ind., a corporation of Delaware No Drawing. Application September 15, 1937,

Serial No. 164,036

1 claim. (01. 75-160) This invention relates to copper alloys particularly of the type susceptible to hardening by heat treatment and by cold working.

An object of the invention is to improve the properties of such copper alloys.

Another object is to provide an alloy which is very susceptible to age-hardening and to cold working.

Other objects of the invention ,will be apparent from the following description taken in connection with the appended claim.

The present invention comprises the combination of elements, methods of manufacture, and the product thereof brought out and exemplified in the disclosure hereinafter set forth, the scope of the invention being indicated in the appended claim.

While apreferred embodiment of the invention is described herein, it is contemplated that considerable variation may be made in the method of procedure and the combination of elements without departing from the spiritof the invention.

According to the present invention improved alloys are formed of copper with one or both of the materials chromium silicide and chromium beryllide by the addition of zirconium.

We are aware that alloys of copper have been described in the prior art, w ich are hardened by an intermetallic compound ormed of silicon or beryllium with chromium. There is,however,

only a limited hardness which can be obtained by using such intermetallic compounds, and the maximum hardness which is obtainable without any cold working does not exceed 125-130 Brinell. This hardness, although it is considerably above the hardness of copper, is not as high as would be desired for a large, number of applications, and we have therefore carried on experiments to further improve the tensile properties, and particularly the hardness and wear resistance of this type of alloy. We have found that by adding substantial quantities of zirconium, such improvement in hardness can be accomplished without serious loss of electrical or thermal conductivity.

The previous art considered the addition of such materials as zinc, tin and aluminum to the above mentioned alloys of the prior art. Such 0 elements are usually classified as solid solution elements. These elements, however, do not take any part in the precipitation caused by the heat treatment described above. They form a space lattice with the copper, in which part of the copper atoms are replaced by atoms of solid solution forming elements.

In our alloy, this atomic structure is entirely changed. The zirconium which we add is eliminated from the copper lattice forming a copperzirconium compound, which is present in the form of sub-microscopical particles, said submicroscopical particles being located in slip planes within the crystals of our improved alloy. This critical location of the new dispersed phase of zirconium is a most contributory factor to the improvements in our new alloy. We have found, for instance, that, with our improved alloy, a Brinell hardness of 160 can be readily obtained, after a double heat treatment, consisting in quenching from a temperature above 700 degrees and aging at a temperature below 700 degrees.

The alloys of the present invention can be obtained in very fine grain structure and with high ductility.

By applying a certain amount of cold work, after quenching and subsequently aging, this hardness can be raised still higher, up to 200 Brinell, and still the electrical conductivity will be above 60% and close to 70%. By taking our improved alloy, quenching it from a temperature range of 800-950 degrees C., and subsequently aging it for several hours at 450 degrees C., and then cold working it to a high hardness, we have found that the additional amount of hardening which is obtained by cold working, is not lost until a temperature of 450 degrees to 500 degrees C. is reached.

With alloys which are hardened only by-lntermetallic compounds formed with chromium approximately 25% of cold work will produce all of the cold work hardening that is possible. The

total amount of this hardening never exceeds 7 more than -30 Brinell points in addition to the hardness obtained by aging. We have also found that the alloys, after the quenching operation, never cold work to a very high hardness. By adding zirconium, in substantial quantities, these disadvantages have been entirely overcome and the material is extremely susceptible to cold working in the quenched condition, as well as to cold working after complete heat treating.

It is contemplated that alloys may be produced according to the invention having ingredients combined in the following range of proportions:

Percent Zirconium 0.05-5 Chromium silicide and/or chromium beryllide 0.1-5 Copper Balance.

It is possible, likewise, to improve by the addition of zirconium the characteristics of other copper alloys, containing chromium silicide and/or chromium beryllide, in the percentages set forth above, if other additional ingredients are present in small quantities, such as silver, zinc, cadmium. calcium, lithium, iron, cobalt, nickel, tin, aluminum, magnesium and manganese.

The alloys can be prepared by well known alloying methods, the hardeners being added as concentrated hardener alloys or as compressed powders or in other ways.

After they are produced the alloys may preferably be given a heat treatment comprising heating to a temperature above 700" C., such as 800-950 C., quenching from that temperature and subsequently aging below 700 C., as at 450 C., for several hours.

The alloys may be cold worked, as previously described, either immediately after quenching or after aging to introduce further improvement of characteristics.

As already stated, these alloys are extremely well adapted to improvement by cold working. In certain applications, such susceptibility to cold working is a factor of prime importance, if, for instance these materials are used as wheels in seam welding operations, which work against a small, formed knurled wheel, in order to keep the contour of the welding face; the pressure exerted by said formed knurled wheel will cold Work our improved alloy and therefore harden it in service and prolong its life many times over that of the alloy of the previous art.

The alloys prepared as indicated above are well suited for the manufacture of castings, such as commutator segments and collector rings for electric machines. The alloys can be used for almost any purpose in which high hardness, high electrical and thermal conductivity are required, in

addition to a high annealing temperature. An improved use of these high strength alloys is in the manufacture of parts for use in internal combustion engines.

In addition, these alloys, on account of the improved wear resistance, at room and elevated temperatures, are suitable for pressure welding electrode tips, welding whels and resistance welding dies in general. They are also useful in current collecting nozzles and arc welding heads. They also may be used for the general'line of hardware in the electrical industry and for such parts as knife switches or other contacts.

While the present invention as to its objects and advantages has been described herein as carried out in specific embodiments thereof, it is not desired to be limited thereby, but it is intended to cover the invention broadly, within the spirit and scope of the appended claim.

What is claimed is:

An age-hardened alloy containing about 0.05- 5% zirconium, 0.1-5% of an intermetallic compound formed from chromium and'silicon, and the remainder substantially all copper, characterized by a combination of high hardness and high electrical conductivity and further characterized by the fact that its hardness and conductivity are not permanently affected by temperatures in order of 500 degrees C.

FRANZ R. HENSEL. EARL I. LARSEN. 

